Abstract: Powdered activated carbon was applied to decolour soybean meal protease hydrolysate by single factor and orthogonal experiments. The factors including pH, quantity of powdered activated carbon, decolouring temperature and adsorption time were investigated in terms of the decolouring rate and the reserved rate of peptide. The results showed that when the conditions were 40mL soybean meal protease hydrolysate, pH4. 0, quantity of powdered activated carbon 0. 6%, decolouring temperature 50℃ and adsorption time 50min, the decolorization effect was distinct but some peptide loss. The decolorizing rate was 86. 52%, the reserved rate of peptide was 75. 04%.